HIVE-29367: prevent Long overflows in ConvertJoinMapJoin #6237
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What changes were proposed in this pull request?
HIVE-29367: fixing overflows in ConvertJoinMapJoin calculations
Why are the changes needed?
ConvertJoinMapJoin does not use StatsUtils.safeAdd()/saveMult() for all its calculations. There are some real life scenarios when it could perform a catastrophic decision to convert a join to a mapjoin after calculating negative size for the 'small" table, resulting in an OOM during query processing
Does this PR introduce any user-facing change?
No
How was this patch tested?
Via unit testing and with load testing on a custom Hive installation based of 4.0x version
You can see the test output generated by the pre-fix code here:
it clearly confirms the decision of perform a mapjoin despite very large volume of data